Radio tube



y 1939- J. s. WELWOOD 2,156,324

RADIO TUBE Filed Feb. 19, 1936 IN VENT OR.

Jose 9&5. Wzzvood BY O gkm ATTORNEY.

Patented May 1939 UNITED STATES PATENT OFFICE RADIO TUBE Application February 19, 1936, Serial No, 64,656

4Claims.

5 have been replaced with metal tube envelopes.

In producing radio tubes with these metal envelopes, many defects have been encountered. The more serious of the defects was the relatively high shrinkage or rejection due to defective metal envelopes or their failure. In some instances, a large percentage, and, in certain instances, as much as about 50% of the radio tubes which were manufactured with metal envelopes failed under test and had to be rejected. This test caused substantial loss and has increased the cost of production. Even the radio tubes which pass the test were objectionable in certain respects. Many of such tubes did not have high and eiflcient emission of electrons. Other disadvantages were the necessity of enameling and baking to avoid rusting, the possibility of rust formation on the inside of the metal envelope, the difficulty of welding the bottom of the metal envelope to a base or header. Many theories have been advanced to explain the high shrinkage orrejection of defective tubes, the low electron emission, the failure in service and the other disadvantages and defects noted hereinabove, but nobody, as far as I am aware, has been able to provide the art with a wholly satisfactory metal envelope which has a low shrinkage or rejection of defective tubes, and an eflicient and good electron emission and which is satisfactory and acceptable to manufacturers of radio tubes, producers of radio sets-and users thereof.

I have discovered a metal envelope for radio tubes which overcomes the disadvantages and difliculties noted hereinabove in connection with prior metal envelopes.

It is an object of the invention to provide a metal radio tube envelope which is satisfactory to produce and which can be assembled in a radio tube structure satisfactorily on an industrial scale with a relatively low percentage of defective tubes.

It is a further object of the invention to provide a metal radio tube envelope containing an alloy of nickel and copper which can be used directly in the manufacture of radio tube envelopes withoutenameling, baking and other operations which have heretofore been used in connection with the enameling of metal tubes.

A further object of the invention is to provide a metal radio tube envelope containing a substantial amount of nickel which is capable of producing an eflicient radio tube and which does not detrimentally affect the electron emission of the completed tube.

It is also within the contemplation of the invention to provide a metal radio tube envelope containing a substantial amount of nickel which has a relatively uniform composition, which has a low rate of evaporation at high temperatures and which is resistant to corrosion.

The invention likewise contemplates providing a metal radio tube envelope containing a substantial amount of nickel which has high strength and rigidity even at high temperatures prevailing during the creation of the vacuum in the manufacture of a radio tube, which has ductility, which is easy to handle and fabricate, which gives a good stamping with a right angle flange, which possesses excellent welding properties and which has a natural silvery appearance capable of resisting rust and capable of imparting to the radio tubes additional sales appeal.

Furthermore, the invention provides a metal radio tube containing a substantial amount of nickel which has clean, smooth surfaces and which is substantially free from gases, including surface and occluded gases, the absence of which is so essential to give a satisfactory and eflicient radio tube.

Other objects and advantages of the invention will become clear from the following description taken in conjunction with the accompanying drawing which illustrates a preferred embodiment of the invention.

The reference character E designates a metal envelope for a radio tube which contains a substantial'amount of nickel. It is preferred to employ a nickel alloy containing about 40% to about of nickel and copper constituting the principal remainder. The envelope comprises an elongated cylindrical shell S at the top of which is a slightly convex crown C. At the bottom of the cylindrical shell is a sharp right angle flange F. On the face of the cylindrical shell, it is preferred to stencil indicia I. It has been found that the best radio tube envelopes made of a nickel copper alloy gave a clear-cut stencil mark which is very legible and which stands out very clearly.

The envelope E is mounted upon a. base B of the radio tube proper. In practice, it has been found that best results are obtained by bonding the flange F of the envelope to the base by means of a weld W. For best results the base B and the weld W are made of the same metal as the envelope E.

Underneath the base is a mounting M of Bakelite or some other appropriate insulating material. As those skilled in the art know, the insulating mounting M carries the conventional elements or members constituting a radio tube. Thus, a plurality of contact prongs K depend from the bottom of the insulating mounting in the usual manner. At the center of the bottom of the mounting a customary post T is provided. As the internal parts of the radio tube are conventional, it will not be necessary to give a detailed description thereof.

In the manufacture of the radio tubes embodying the present invention, a nickel containing envelope is drawn in dies having the proper shape. The base is drawn and the elements of the radio tube are assembled in the usual manner. The flange F of envelope E is bonded to base B by means of weld W. The tube is then heated up to approximately 2000 F. and a vacuum is created within the envelope. When the desired vacuum is produced, the radio tube is sealed. As the nickel copper alloy and as other .metal tube envelopes containing a substantial amount of nickel have clean, smooth surfaces and are relatively free from surface and occluded gases, the formation of the vacuum is facilitated. In testing the present improved tubes with metal envelopes containing a substantial amount of nickel, it has been found that the shrinkage has been reduced to a very low percentage. The electron emission of these tubes has been good and efficient.

In carrying the present invention into practice, it has been found that although the aforesaid nickel -copper alloys are preferred, satisfactory results can be obtained by using a nickeliron-chromium alloy, especially one containing about 6% to about 10% nickel, about 17% to about 20% chromium and the balance principally iron; or one containing about 70% to about 85% nickel, about 10% to about 30% of chromium and the balance substantially iron, or preferably one containing about 78% Ni, about 14% Cr, and the balance principally iron. Nickel or nickel alloys containing at least 20% to about 30% or more of nickel and copper constituting substantially the remainder can likewise be used with good results and are to be considered within the purview of the present invention.

In view of the fact that the alloys used accord ing to the present invention are non-magnetic at mildly elevated temperatures and have high electrical resistivity, it is easier to heat internal parts by induction in a manner similar to that employed in the manufacture of glass tubes.

It is to be observed that the present invention overcomes the difficulty with prior iron envelopes which when exposed to moisture will rust and may liberate hydrogen which will slowly diffuse through the steel envelope and impair the vacuum.

Furthermore, the present invention provides a metal envelope or a radio tube constituted of nickel-copper alloys having low thermal conductivity which permits the localization of heat more definitely in selected areas of the envelope and which permits the use of higher temperatures in the upper part of the envelope during exhaust without prematurely firing the getter.

Moreover, the present invention provides a metal envelope for a radio tube constituted principally of nickel which is free from the defects of the prior iron or steel envelopes including the defect that the internal parts of prior tubes could not be heated effectively by induction during out-gassing due to the high magnetic permeability of prior envelopes and, consequently, defective tubes were produced. Similarly, the prior iron and steel envelopes possessed low electrical resistivity which made inductive heating prohibitively expensive although this method of'heating is the best method for controlling the temperature of the internal parts of the radio tube. Then, again, prior steel envelopes had the disadvantage that the oxide thereon was not adherent and flaked off, even after enamelling thereby exposing the surface of the steel envelope to the atmosphere and to rusting. Due to the relatively low tensile strength of iron and mild steel at elevated temperatures prior envelopes had to be made of thicker metal whereas the present metal envelopes may be made of thinner nickel-bearing material.

It is likewise to be noted that the present invention provides a metal envelope constituted of a nickelbearing metal, especially nickel-copper alloys, possessing relatively high electrical resistance and lower-permeability and better adapted for inductive heating of the internal tube parts than prior tubes.

The invention also contemplates the provision of a metal envelope constituted of a nickel-bearing metal, such as nickel-copper alloys which possesses the advantage that an attractive oxide film is formed on the outside surface of the envelope without any additional operation or expense and that the oxide film is extremely adherent.

It is likewise within the contemplation of the invention to provide a nickel-bearing metal, especially a nickel-copper alloy, which will not flash like prior iron and steel shells. This flashing of prior iron and steel shells or envelopes has caused short circuits to occur within the radio tube. In some factories the losses due to rejection from flashes are as high as about 5% or so. The elimination of flash losses by the present invention is another feature thereof.

I claim:

1. As a new article of manufacture, a metal envelope for a radio tube comprising a tubular portion closed at one end and provided at the other end with a flange adapted to be welded to a metal base member, said envelope being constituted of a nickel alloy consisting substantially of about 20% to about 80% of nickel and the balance consisting principally of copper.

2. As a new article of manufacture, a metal envelope for a radio tube comprising a tubular portion closed at one end and provided at the other end with a flange adapted to be welded to a metal base member, said envelope being constituted of a nickel alloy consisting substantially of about 40% to about 80% of nickel and the balance consisting principally of copper.

3. As a new article of manufacture, a metal envelope for a radio tube comprising a cylindrical shell having a crown at the top thereof and a portion at the bottom thereof adapted to be welded to a metal base member, said shell being constituted of any alloy consisting substantially of about 20% to about 80% of nickel and the balance consisting principally of copper.

4. As a new article of manufacture, a metal envelope for a radio tube which comprises a metal base having electrodes and contact prongs insulated therefrom, and a metal-bearing cylindrical shell welded to said base and forming a vacuum-tight chamber around said electrodes, said base and said shell being substantially wholly constituted of an alloy consisting substantially of about 20% to about 80% of nickel, and the balance consisting principally of copper.

JOSEPH S. WELWOOD. 

